JP6453581B2 - Power supply device, power supply system, and power supply method - Google Patents

Description

  The present invention relates to a power supply device, a power supply system, and a power supply method. More specifically, the present invention relates to a power supply device that supplies power generated by a distributed power source such as a fuel cell, a power supply system including such a power supply device, and a power supply in such a system. It is about the method.

  In recent years, a system in which a plurality of distributed power sources such as a solar cell and a fuel cell are connected as a power generation device and electric power generated by these power generation devices has been studied. As such a power generation apparatus used as a distributed power source, for example, fuel cells such as a polymer electrolyte fuel cell (PEFC) and a solid oxide fuel cell (SOFC) are known.

  Currently, in Japan, power generated using a distributed power source such as the fuel cell described above cannot be sold to the grid. For this reason, a power conditioner (inverter) in a current power supply system controls to reduce or stop the supply of power when a reverse power flow to a power system generated by a distributed power source such as a fuel cell is detected. . Therefore, in a system that operates by connecting a plurality of these distributed power sources, when a reverse power flow is detected, the outputs of the plurality of distributed power sources are controlled so that the power supplied as a whole system does not flow backward. (Refer to Patent Document 1).

JP 2002-247765 A JP 2000-92719 A

  By the way, for example, an operation in which the power conditioner is disconnected from the system during operation due to a power failure or the like and is continued in a state where the power supplied from the power conditioner and the power consumption of the load are balanced is referred to as a single operation. In this way, it becomes necessary to stop the power supply from the power conditioner from the viewpoint of safety of workers and the like when the operation becomes independent. As a method for detecting such an isolated operation, for example, there is a voltage phase jumping method, which is a passive detection method using a change in voltage phase due to a load during an isolated operation (see Patent Document 2). The detection by this method may take a certain amount of time.

  As described above, since the power generated by the fuel cell cannot be sold to the grid, the power conditioner controls so that the supplied power does not exceed the power consumption of the load. At this time, the power conditioner performs control so that the power from the system has a slight forward current in order to prevent generation of power that flows backward to the system.

  However, when the power conditioner is operated independently, the current flowing between the system and the system is not detected. For this reason, the power conditioner suppresses the electric power supplied from the power conditioner in an attempt to increase the forward current. When the power conditioner suppresses the supply of power in this way, the voltage (link voltage) of the DC link that couples the DC / DC converter and the DC / AC inverter in the power conditioner decreases. When the link voltage decreases, various problems occur, for example, it becomes impossible to properly control the power supplied by the power conditioner.

  Therefore, an object of the present invention is to provide a power supply device capable of preventing a decrease in link voltage even when the operation is performed so that the power output from the distributed power source does not flow backward to the grid, An object is to provide a power supply system and a power supply method.

The invention according to the first aspect to achieve the above object is
And interconnection to the system, a power supply apparatus for converting DC power from the dispersed type power supply to AC power,
The power supply device includes a control unit that controls the AC power according to a current flowing between the power supply device and the system.
The control unit is configured such that the peak of the current (A3) supplied from the power supply device is less than a first threshold (for example, 1A), and the absolute current (CT) flowing between the power supply device and the system When the value is less than a second threshold value (for example, 0.1 A), control is performed so as to maintain the power output from the distributed power source.

  Moreover, the said control part may perform such control when the electric power (CT * V3) between the said electric power supply apparatus and the said system | strain is more than a 3rd threshold value (for example, -50W).

In addition, the control unit increases the power output from the distributed power source when the power (CT × V3) between the power supply device and the system is less than the third threshold (for example, −50 W). You may control to make it.

In addition, the control unit is configured such that the peak of the current (A3) supplied from the power supply device is equal to or higher than the first threshold (for example, 1A), or a current (CT that flows between the power supply device and the system) ) May be controlled so as to reduce the power output from the distributed power source when the absolute value of the power is greater than or equal to the second threshold value (for example, 0.1 A).

  Moreover, the said control part may perform such control, when the electric power (CT * V3) between the said electric power supply apparatus and the said system | strain is more than a 4th threshold value (for example, -40W).

  In addition, the control unit maintains the power output from the distributed power source when the power (CT × V3) between the power supply device and the system is less than the fourth threshold (for example, −40 W). You may control to do.

The invention according to the second aspect to achieve the above object is
A power supply device and interconnection to the system, to convert the DC power from the dispersed type power supply to AC power,
A current sensor for detecting a current (CT) flowing between the power supply device and the system;
A power supply system comprising:
In the power supply device, the peak of the current (A3) supplied from the power supply device is less than a first threshold (for example, 1A), and the absolute value of the current (CT) detected by the current sensor is a second value. When it is less than a threshold value (for example, 0.1 A), control is performed so as to maintain the power output from the distributed power source.

The invention according to the third aspect for achieving the above object is:
A power supply device and interconnection to the system, to convert the DC power from the dispersed type power supply to AC power,
A current sensor for detecting a current (CT) flowing between the power supply device and the system;
A power supply method in a power supply system including:
In the power supply device, the peak of the current (A3) supplied from the power supply device is less than a first threshold (for example, 1A), and the absolute value of the current (CT) detected by the current sensor is a second value. When it is less than a threshold value (for example, 0.1 A), control is performed so as to maintain the power output from the distributed power source.

  According to the present invention, when operating so that the power output from the distributed power source does not flow backward to the system, the power supply device and the power supply that can prevent the link voltage from being lowered even when the power supply is in a single operation state. A system and a power supply method can be provided.

1 is a functional block diagram schematically showing a power supply system according to an embodiment of the present invention. It is a conceptual diagram explaining control of the conventional power supply apparatus. It is a conceptual diagram explaining control of the conventional power supply apparatus. It is a flowchart explaining operation | movement of the electric power supply apparatus which concerns on embodiment of this invention. It is a conceptual diagram explaining control of the electric power supply apparatus which concerns on embodiment of this invention. It is a conceptual diagram explaining control of the electric power supply apparatus which concerns on embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a functional block diagram schematically showing a power supply system including a power supply device according to an embodiment of the present invention. In the following description, description of elements and function units well known in the art will be simplified or omitted as appropriate.

  As shown in FIG. 1, the power supply system 1 according to the embodiment of the present invention includes a power supply device 10, a DC power supply 30, and a current sensor 40. In FIG. 1, an example in which the power supply system 1 includes a power supply device 10 to which one DC power supply 30 that is a distributed power supply is connected is shown. However, the power supply system 1 according to the present embodiment may be configured to include an arbitrary number of power supply devices configured as the power supply device 10 and distributed power sources configured as the DC power supply 30 and the like. it can. Moreover, although the example in case the electric power supply system 1 is single phase 2 wire connection is shown in FIG. 1, this embodiment is not limited to such an example, for example, single phase 3 wire connection or 3 phase A three-wire connection may be used.

  As shown in FIG. 1, the power supply device 10 is connected to a DC power source 30 that is a distributed power source. The power supply device 10 controls the power output from the DC power supply 30 and supplies it to the load 200. Here, the power supply device 10 converts the power supplied to the load 200 in connection with the system 100 from direct current to alternating current. Thus, the structure for the power supply device 10 to convert power can adopt the same structure as that of a conventional power conditioner. Details of control and configuration performed by the power supply device 10 will be described later.

  The DC power supply 30 is connected to the power supply device 10 and outputs power supplied to the load 200 in connection with the system 100. Here, the system 100 can be a general commercial power system (grid). The DC power supply 30 can be configured to include various fuel cells such as a polymer electrolyte fuel cell (PEFC) or a solid oxide fuel cell (SOFC). In particular, in the present embodiment, it is preferable that the DC power supply 30 generate power that cannot be generated by selling the generated power to the system, that is, cannot be reversely flowed.

  Here, “electric power that cannot be reversely flowed” is electric power based on energy supplied from the infrastructure, such as electric power generated by a fuel cell, for example. Unacceptable power. Therefore, in the present embodiment, the DC power source 30 is a power generation unit different from that capable of selling the generated power to the system, such as a power generation unit including a solar cell that performs solar power generation. Is preferred. Hereinafter, an example in which the DC power supply 30 is an SOFC that generates DC power will be described. However, the distributed power source according to the present invention is not limited to the SOFC that generates direct-current power, and typically includes various power generation devices including a fuel cell, or a storage battery that can charge and discharge power. A distributed power source may be used.

  When the DC power source 30 is configured by SOFC, the DC power source 30 can generate electric power by a fuel cell power generation device that electrochemically reacts gases such as hydrogen and oxygen supplied from the outside, and can output the generated electric power. In the present embodiment, the DC power supply 30 starts operation upon receiving power from the system 100 at the time of startup, but operates after receiving the power from the system 100, that is, is capable of independent operation. May be. In the present embodiment, the DC power supply 30 appropriately includes other functional units such as a reforming unit as necessary so that the DC power supply 30 can be operated independently. In the present embodiment, the DC power supply 30 can be configured by a generally well-known fuel cell, and therefore a more detailed description of the fuel cell is omitted.

  The power generated by the DC power supply 30 can be supplied to various loads 200 that consume power through the power supply device 10. Here, in an actual house or the like, the power supplied from the power supply device 10 is supplied to the load 200 after passing through a distribution board or the like, but such members are omitted. The load 200 can be various devices such as home appliances used by the user, to which power is supplied from the power supply system 1. In FIG. 1, the load 200 is shown as one member, but is not limited to one member and can be any number of various devices.

  The power supply system 1 according to the present embodiment may include a plurality of power supply devices and a set of distributed power sources that output power to the power supply devices. When configuring a power supply system including a plurality of power supply devices in this way, the plurality of power supply devices are supplied from each of the plurality of power supply devices so that power is input from each connected distributed power source. It is preferable that the electric power to be connected is connected.

  Furthermore, as shown in FIG. 1, in the power supply system 1, a current sensor 40 is connected to the power supply device 10. The current sensor 40 can be, for example, a CT (Current Transformer). However, any element can be adopted as long as it can detect current.

  The current sensor 40 detects a current flowing between the power supply device 10 and the system 100. Thereby, the power supply device 10 can determine whether or not the power supplied from the power supply system 1 is flowing backward to the grid 100. For this reason, as shown in FIG. 1, the current sensor 40 is disposed at a position for detecting the power flowing through the system 100 after being supplied to the load 200 from the power supplied from the power supply device 10.

  The value of the current detected by the current sensor 40 is notified directly or indirectly to the power supply device 10 by wireless or wired communication. The power supply device 10 can calculate the reverse power flow from the current detected by the current sensor 40 and the AC voltage supplied from the power supply device 10. Hereinafter, for the sake of explanation, the value of the current detected by the current sensor 40 is referred to as CT.

  Next, the power supply device 10 according to the present embodiment will be described in more detail.

  As shown in FIG. 1, the power supply device 10 includes a DC / DC converter 12, an inverter 14, and a control unit 16.

  The DC / DC converter 12A performs adjustment such as stepping up or stepping down the direct current power output from the direct current power supply 30. The inverter 14 converts the DC power whose voltage is adjusted by the DC / DC converter 12 into AC. Since the DC / DC converter 12 and the inverter 14 can have a generally well-known configuration, a more detailed description is omitted.

  The control unit 16 controls and manages the entire power supply device 10 including each functional unit of the power supply device 10. The control part 16 can be comprised by a microcomputer or a processor (CPU) etc., for example. Moreover, the control part 16 is demonstrated below as what is also provided with the memory which memorize | stores various programs and various information. This memory also stores algorithms for performing data analysis and various arithmetic processes performed by the control unit 16, and various reference tables such as a lookup table (LUT).

  In particular, in the present embodiment, the control unit 16 can control the AC power supplied from the power supply device 10 by controlling the DC power input from the DC power supply 30. In order to perform such control, the control unit 16 is connected to the DC / DC converter 12 and the inverter 14 by a control line as shown in FIG.

  As shown in FIG. 1, when the current sensor 40 is connected to the power supply device 10, it is preferable that the current sensor 40 is connected to the control unit 16. With such a connection, the control unit 16 controls the DC power output from the DC power supply 30 connected to the power supply device 10 according to the current flowing between the power supply device 10 and the system 100, respectively. be able to.

  As shown in FIG. 1, the power supply device 10 also includes an ammeter 21, a voltmeter 22, a voltmeter 23, a link capacitor 24, an ammeter 25, and a voltmeter 26.

  The ammeter 21 measures the current value of the DC power output from the DC power supply 30. Hereinafter, the value of the current measured by the ammeter 21 is denoted as A1. The voltmeter 22 measures the voltage value of DC power input from the DC power supply 30 to the power supply device 10. Hereinafter, the value of the voltage measured by the voltmeter 22 is denoted as V1.

  The voltmeter 23 measures the voltage value of the DC power after being adjusted by the DC / DC converter, that is, the voltage value of the link capacitor 24. Hereinafter, the voltage value measured by the voltmeter 23 is denoted as V2. The link capacitor 24 is a capacitor that can cope with fluctuations in power by accumulating power output from the DC power supply 30 to some extent.

  The ammeter 25 measures the current value of the electric power output after the inverter 14 converts from direct current to alternating current. Hereinafter, the value of the current measured by the ammeter 25 is referred to as A3. The voltmeter 26 measures the voltage value of the electric power after the inverter 14 converts from direct current to alternating current. Hereinafter, the voltage value measured by the voltmeter 26 is referred to as V3.

  Any ammeter can be adopted as the ammeter 21 and the ammeter 25 as long as the current value can be measured. Similarly, any voltmeter 22, voltmeter 23, and voltmeter 26 can be used as long as they can measure voltage values. In FIG. 1, the ammeter 21, the current sensor 40, and the ammeter 25 each have a direction indicated by an arrow in the vicinity as a positive direction. Therefore, in FIG. 1, the flow of reverse power flow to the grid is in the positive direction, and the flow of reverse power flow from the grid is in the negative direction.

  Next, operation | movement of the electric power supply apparatus 10 which concerns on this embodiment is demonstrated.

  In the present embodiment, the power supply device 10 is linked even if it is in a single operation state due to a power failure or the like during operation so that power that cannot be sold, such as a fuel cell, does not flow backward. Control is performed so that the voltage does not decrease.

  Hereinafter, in order to describe the control according to the present embodiment, first, an operation assumed when a conventional power conditioner is used without using the power supply device 10 will be described. Here, the “conventional power conditioner” can have a device configuration similar to that of the power supply system 1 shown in FIG. 1, but the control thereof is the control of the power supply device 10 according to the present embodiment. This is different from the control by the unit 16. In the following description, the current values and voltage values measured by each ammeter and voltmeter are the same as the symbols described in FIG.

  2 and 3 are diagrams for explaining the operation of a conventional power conditioner. Both FIG. 2 and FIG. 3 schematically show temporal changes in current value, voltage value, power value, and the like at each location. From left to right, ie, from time (1) to time (5), time is shown as elapses.

  FIG. 2A is a diagram showing the output current (A3) of the inverter measured at the position of the ammeter 25. FIG. FIG. 2B is a diagram showing the grid current (CT) measured at the position of the current sensor 40. FIG. 2C is a diagram showing an AC voltage (V3) measured at the position of the voltmeter 26.

  FIG. 3A shows the inverter output represented by the product of the inverter output current (A3) measured at the position of the ammeter 25 and the AC voltage (V3) measured at the position of the voltmeter 26. It is a figure which shows electric power (A3 * V3). At the same time, FIG. 3A shows the system power represented by the product of the system current (CT) measured at the position of the current sensor 40 and the AC voltage (V3) measured at the position of the voltmeter 26. (CT × V3) is also shown.

  FIG. 3B is a diagram showing the link voltage (V 2) measured at the position of the voltmeter 23. At the same time, FIG. 3B also shows the input voltage (V1) measured at the position of the voltmeter 22. This input voltage indicates the voltage of power output from the DC power supply 30 and input to the DC / DC converter 12.

  2 and 3, it is assumed that the power conditioner starts operation from the time point (1), and a power failure or the like occurs at the time point (3) to start the single operation.

  When the single operation is started at the time point (3), the grid current (CT) becomes 0A as shown in FIG. 2 (B), so there is no forward current from the grid nor reverse current to the grid. It becomes a state. As shown in FIG. 2 (B), during the single operation (after time (3)), no current flows on the system side.

  As described above, when the grid operation is performed, the power conditioner has a slight forward power flow state. When the system current (CT) is close to 0 A, the power conditioner has an input voltage as shown in FIG. By increasing (V1), the input DC power is suppressed, and the power of the forward power flow is increased. When the input DC power decreases, the link voltage (V2) also decreases. Therefore, the power conditioner decreases the inverter output current (A3) in an attempt to keep the link voltage (V2) constant.

  As shown in FIG. 2A, during the single operation (after time (3)), when load following is started, the forward output power from the system is increased, and therefore the inverter output current (A3) starts to be suppressed. . During the single operation (after time (3)), since the voltage is not fixed, when the inverter output current (A3) decreases as shown in FIG. 2 (A), the alternating current as shown in FIG. The voltage (V3) also decreases. As described above, since the AC voltage (V3) and the inverter output current (A3) are simultaneously reduced, the inverter output power (A3 × V3) is reduced at a higher speed than when the single operation is not performed.

  Eventually, when the time point (4) is reached and the inverter output power (A3 × V3) is suppressed to 0 W as shown in FIG. 3 (A), the inverter output current (A3) becomes as shown in FIG. 2 (A). Less than 0 A (after time (5)). Here, during the independent operation, when the inverter output current (A3) shown in FIG. 2 (A) becomes negative, the AC voltage (V3) shown in FIG. 2 (C) also becomes negative.

  Thus, after the time point (5) when both A3 and V3 become negative, the product of the inverter output power (A3 × V3) becomes positive as shown in FIG. That is, when the inverter output current (A3) is decreased to increase the link voltage (V2), the inverter output power (A3 × V3) increases. Conversely, when the inverter output current (A3) is increased to decrease the link voltage (V2), the inverter output power (A3 × V3) is decreased. For this reason, as shown in FIG.3 (B), a power conditioner will control link voltage (V2) contrary to a user's intention as a result.

  In the case of the example shown in FIGS. 2 and 3, the power output from the DC power source 30 at time (5) is already 0 W, and there is no power source that increases the link voltage (V2). The voltage (V2) decreases rapidly. When the link voltage (V2) decreases in this way, the input voltage (V1) does not become larger than the link voltage (V2) as shown in FIG. 3B (after time (6)). For this reason, the input voltage (V1) cannot be controlled to the target value. When the link voltage (V2) decreases and becomes lower than the voltage of the DC power supply, for example, current flows from the DC power supply even when the booster switch of the DC / DC converter 12 is off, and in some cases an overcurrent flows. Inconvenience is also assumed.

  In order to avoid such inconvenience, in the present embodiment, the control unit 16 of the power supply device 10 calculates the power at the position from the current value (CT) at the position of the current sensor 40, and a slight forward flow occurs. The electric power input from the DC electric power 30 is adjusted so as to be in a state of being in operation. Specifically, this power adjustment is performed by the control unit 16 controlling the DC / DC converter 12 to change the operating voltage (input voltage (V1)) of the DC power supply 30. Further, the control unit 16 controls the power supply device 10 so that the link voltage (V2) becomes constant. Thereby, the electric power output from the DC power source 30 is pushed out to the AC side and consumed by the load 200. Hereinafter, operation | movement of the electric power supply apparatus 10 which concerns on this embodiment is demonstrated in detail.

  FIG. 4 is a flowchart for explaining the operation of the power supply device 10 according to the present embodiment. FIG. 4 illustrates the control performed by the control unit 16 in the power supply device 10 according to the present embodiment.

  5 and 6 are diagrams for explaining the operation of the power supply device 10 according to the present invention. 5 and 6 schematically show temporal changes in current values, voltage values, power values, and the like at each location, as in FIGS. 2 and 3. 5 and 6 also show that time elapses from left to right, that is, from time (1) to time (4). 5 and 6, it is assumed that the power supply device 10 starts operation from the time point (1), and a power failure or the like occurs at the time point (3) to start the single operation.

  5A shows the output current (A3) of the inverter measured by the ammeter 25, FIG. 5B shows the system current (CT) measured by the current sensor 40, and FIG. 5C shows the voltmeter. The alternating voltage (V3) which 26 measures is shown.

  FIG. 6A shows inverter output power (A3 × V3) represented by the product of the inverter output current (A3) measured by the ammeter 25 and the AC voltage (V3) measured by the voltmeter 26. FIG. 6A also shows system power (CT × V3) represented by the product of the system current (CT) measured by the current sensor 40 and the AC voltage (V3) measured by the voltmeter 26.

  FIG. 6B is a diagram showing the link voltage (V2) measured by the voltmeter 23. FIG. 6B also shows the input voltage (V1) measured by the voltmeter 22. This input voltage indicates the voltage of power output from the DC power supply 30 and input to the DC / DC converter 12.

  As shown in FIG. 4, when the operation of the power supply device 10 according to the present embodiment starts, the control unit 16 sets a predetermined threshold (third value) such that the value of the system power (CT × V3) is −50 W, for example. It is determined whether or not (threshold) or more (step S11). As this predetermined threshold value, it is preferable to set an appropriate threshold value as a preceding stage in which a reverse power flow to the grid 100 may occur if this value is exceeded. In other words, this predetermined threshold value is preferably set as a value that assumes that there is no possibility of generating reverse power flow immediately if the system power (CT × V3) does not exceed this value. In the following description, it is assumed that the predetermined threshold is −50 W. Note that the system power (CT × V3) being −50 W or more means that the forward power flow is 50 W or less.

  When the system power (CT × V3) is not −50 W or more in step S11, the output power of the DC power supply 30 can be increased, so the control unit 16 decreases the input voltage (V1) by a predetermined value (step S12). ). The predetermined value is preferably set to an appropriate value in accordance with the characteristics of the change in the output power of the DC power supply 30 based on the change in the input voltage (V1). In the power supply device 10, the output power of the DC power supply 30 (power input from the DC power supply 30 to the DC / DC converter 12) can be increased by reducing the input voltage (V 1).

  The process flow of step S11 and step S12 corresponds to the time point (1) to the time point (2) in FIGS. As shown in FIG. 6A, the system power (CT × V3) does not reach −50 W at this time, so the control unit 16 sets the input voltage (V1) as shown in FIG. Reduce.

  When the system power (CT × V3) is −50 W or more in step S11, the control unit 16 determines whether or not the peak of the inverter output current (A3) is less than a predetermined threshold (first threshold) such as 1A, for example. Is determined (step S13). As this predetermined threshold value, it is preferable to set an appropriate threshold value as a preceding stage where the peak of the inverter output current (A3) may soon turn to a negative value when it falls below this value. That is, the predetermined threshold value is set as a value that assumes that the inverter output current (A3) is not likely to become a negative value immediately if the peak of the inverter output current (A3) does not fall below this value. Is preferred. In the following description, it is assumed that the predetermined threshold is 1A.

  When the peak of the inverter output current (A3) is not less than 1A in step S13, the control unit 16 determines whether or not the system power (CT × V3) is equal to or greater than a predetermined threshold (fourth threshold) such as −40 W, for example. Is determined (step S14). That is, in step S14, it is determined whether or not system power (CT × V3) ≧ −40 W or −40 W> system power (CT × V3) ≧ −50. It is preferable to set an appropriate threshold value as a preceding stage that may cause a reverse power flow to the grid 100 if this predetermined threshold value is exceeded. In the following description, it is assumed that the predetermined threshold is −40W. Note that the system power (CT × V3) being −40 W or more means that the forward power flow is 40 W or less. Therefore, by setting the threshold value of the grid power (CT × V3) in step S11 and step S14, the power supply device 10 maintains the forward power flow from the grid between the set threshold values. For this reason, these threshold values can be set as an upper limit and a lower limit of a range in which forward flow is desired to be controlled.

  The flow of processing from step S13 to step S14 corresponds to time (2) to time (4) in FIGS. From time (2) to time (4), as shown in FIG. 5 (A), the peak of the inverter output current (A3) is 1 A or more.

  When the system power (CT × V3) is not −40 W or more in step S14, the control unit 16 maintains the input voltage (V1) (step S15). Thereby, the output power of the DC power supply 30 (power input to the DC / DC converter 12 from the DC power supply 30) can also be maintained.

  The flow of processing from step S14 to step S15 corresponds to time (2) to time (3) in FIGS. From time (2) to time (3), as shown in FIG. 6 (A), the grid power (CT × V3) is not −40 or more (−50 W). In this case, as shown in FIG. 6B, the input voltage (V1) is maintained.

  When the system power (CT × V3) is −40 W or more in step S14, the control unit 16 increases the input voltage (V1) by a predetermined value in order to reduce the output power of the DC power supply 30 (step S16). This predetermined value is also preferably set to an appropriate value according to the characteristics of the change in the output power of the DC power supply 30 based on the change in the input voltage (V1). In the power supply device 10, the output power of the DC power supply 30 (power supplied from the DC power supply 30 to the DC / DC converter 12) can be reduced by increasing the input voltage (V1).

  The flow of processing from step S14 to step S16 corresponds to time (3) to time (4) in FIGS. 5 and 6. From time (3) to time (4), as shown in FIG. 6 (A), the system power (CT × V3) is −40 or more (0 W). In this case, as shown in FIG. 6B, the input voltage (V1) is increased.

  On the other hand, when the peak of the inverter output current (A3) is less than 1A in step S13, the control unit 16 sets a predetermined threshold value (second threshold value) such that the absolute value of the system current (CT) is, for example, 0.1A. It is determined whether it is less than (step S17). That is, in step S17, it is determined whether or not the power supply device 10 is assumed to be in a single operation state. As described above, for example, if the power supply device 10 is in a single operation state due to a power failure or the like, the current value (CT) measured by the current sensor 40 becomes substantially zero. Therefore, it is preferable to set a value close to zero as the predetermined threshold here. In the following description, it is assumed that the predetermined threshold is 0.1A. Moreover, since it can be positive and negative depending on the direction of current flow, it is preferable to make a determination based on the absolute value of the grid current (CT).

  When the absolute value of the grid current (CT) is not less than 0.1 A in step S17, the power supply device 10 may not be in an independent operation. Therefore, the control unit 16 proceeds to step S14 and continues the process. . On the other hand, when the absolute value of the grid current (CT) is less than 0.1 A in step S17, it is assumed that the power supply device 10 is operating independently, so the control unit 16 proceeds to step S15 and performs processing. To continue.

  The flow of processing from step S17 to step S15 corresponds to the time point (4) and after in FIG. 5 and FIG. After time (4), the input voltage (V1) is maintained as shown in FIG. 6 (B). Therefore, the inverter output current (A3) does not decrease any more as shown in FIG. 5 (A), and the link voltage (V2) does not decrease as shown in FIG. 6 (B). Thus, according to the present embodiment, since the inverter output current (A3) does not become negative, the output power is controlled contrary to the user's intention as in the conventional case, and the link voltage becomes unstable. Can be prevented.

  The process described with reference to FIG. 4 is preferably a process that the control unit 16 periodically repeats in order to control the input voltage (V1).

  As described above, in the present embodiment, the DC power from the DC power supply 30 is converted into AC power connected to the system 100. In the present embodiment, the control unit 16 controls the AC power according to the current flowing between the power supply device 10 and the system 100. Here, the control unit 16 performs control so as to maintain the power output from the DC power supply 30 under a predetermined condition. The predetermined condition is that the peak of the current (A3) supplied from the power supply device 10 is less than a first threshold (for example, 1A), and the current (CT) that flows between the power supply device 10 and the system 100 Is an absolute value less than a second threshold (for example, 0.1 A).

  Here, the control unit 16 may perform such control when the power (CT × V3) between the power supply device 10 and the system 100 is greater than or equal to a third threshold (for example, −50 W). Moreover, the control part 16 reduces the electric power output from the DC power supply 30, when the electric power (CT * V3) between the electric power supply apparatus 10 and the system | strain 100 is less than the said 3rd threshold value (for example, -50W). You may control as follows.

  Further, the control unit 16 may perform control so as to increase the power output from the DC power supply 30 under a predetermined condition. This predetermined condition is that the peak of the current (A3) supplied from the power supply device 10 is greater than or equal to the first threshold value (for example, 1A), or the current flowing between the power supply device 10 and the system 100 (CT ) When the absolute value is equal to or greater than the second threshold value (for example, 0.1 A).

  Moreover, the control part 16 may perform such control when the electric power (CT * V3) between the electric power supply apparatus 10 and the system | strain 100 is more than a 4th threshold value (for example, -40W). Further, the control unit 16 maintains the power output from the DC power supply 30 when the power (CT × V3) between the power supply device 10 and the system 100 is less than the fourth threshold value (for example, −40 W). You may control as follows.

  According to the present embodiment, current and voltage at various places can be maintained in a stable state when it is detected that the state is a single operation while preventing the occurrence of reverse power flow during normal interconnection operation. Therefore, according to the present embodiment, the link voltage (V2) can be maintained without being lowered, and an inconvenience that an overcurrent flows is avoided. Moreover, according to this embodiment, even if it takes time until it is detected that the vehicle is in a single operation state, currents and voltages at various places can be kept stable. Further, according to the present embodiment, the system current (CT) is detected as 0 A even when the current sensor 40 is disconnected or dropped, for example, other than during single operation. However, even in such a case, since the power output from the DC power supply 30 is controlled to near 0 W, the reverse power flow to the system 100 is prevented.

  Although the present invention has been described based on the drawings and examples, it should be noted that those skilled in the art can easily make various variations and modifications based on the present disclosure. Therefore, it should be noted that these variations and modifications are included in the scope of the present invention. For example, the functions included in each functional unit, each means, each step, etc. can be rearranged so that there is no logical contradiction, and a plurality of functional units, steps, etc. are combined or divided into one. It is possible. In addition, each of the embodiments of the present invention described above is not limited to being performed faithfully to each of the embodiments described above, and is implemented by appropriately combining the features or omitting some of the features. You can also.

  In addition, the present invention can be implemented not only as an invention of the power supply device 10 but also as an invention of a power supply system including a power supply device such as the power supply device 10C. In this case, in the system, the power supply device 10 performs control so as to maintain the power output from the DC power supply 30 under a predetermined condition. The predetermined condition is that the peak of the current (A3) supplied from the power supply device 10 is less than a first threshold (for example, 1 A) and the absolute value of the current (CT) detected by the current sensor 40 is the second. Is less than the threshold value (for example, 0.1 A).

  Furthermore, the present invention can also be implemented as a power supply method in the power supply system as described above.

DESCRIPTION OF SYMBOLS 1 Electric power supply system 10 Electric power supply apparatus 12 DC / DC converter 14 Inverter 16 Control part 21, 25 Ammeter 22, 23, 26 Voltmeter 24 Link capacitor 30 DC power supply 40 Current sensor 100 System 200 Load

Claims (8)

And interconnection to the system, a power supply apparatus for converting DC power from the dispersed type power supply to AC power,
The power supply device includes a control unit that controls the AC power according to a current flowing between the power supply device and the system.
When the peak of the current supplied from the power supply device is less than the first threshold and the absolute value of the current flowing between the power supply device and the system is less than the second threshold, A power supply device that controls to maintain power output from the distributed power source.   The said control part is an electric power supply apparatus which performs control of Claim 1 when the electric power between the said electric power supply apparatus and the said system | strain is more than a 3rd threshold value. The said control part is controlled so that the electric power output from the said distributed power supply may be increased when the electric power between the said electric power supply apparatus and the said system | strain is less than the said 3rd threshold value. Power supply equipment. The control unit is configured such that a peak of current supplied from the power supply device is equal to or greater than the first threshold value, or an absolute value of current flowing between the power supply device and the system is equal to or greater than the second threshold value. The power supply device according to any one of claims 1 to 3, wherein control is performed so as to reduce power output from the distributed power source.   The said control part is an electric power supply apparatus which performs control of Claim 4 when the electric power between the said electric power supply apparatus and the said system | strain is more than a 4th threshold value.   5. The control unit according to claim 4, wherein when the power between the power supply device and the system is less than the fourth threshold value, the control unit controls to maintain the power output from the distributed power source. Power supply equipment. A power supply device and interconnection to the system, to convert the DC power from the dispersed type power supply to AC power,
A current sensor for detecting a current flowing between the power supply device and the system;
A power supply system comprising:
The power supply device is configured such that when the peak of the current supplied from the power supply device is less than a first threshold and the absolute value of the current detected by the current sensor is less than a second threshold, the distributed power supply A power supply system that controls to maintain the output power. A power supply device and interconnection to the system, to convert the DC power from the dispersed type power supply to AC power,
A current sensor for detecting a current flowing between the power supply device and the system;
A power supply method in a power supply system including:
In the power supply device, when the peak of the current supplied from the power supply device is less than a first threshold and the absolute value of the current detected by the current sensor is less than a second threshold, the distributed power source A power supply method for controlling to maintain output power.

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